Interposer assembly.

ABSTRACT

An interposer assembly includes a dielectric plate having a plurality of contact passages extending through the plate with a contact in each passage. Each contact includes a pair of laterally spaced contact points at the top and bottom of the plate. Sandwiching of the interposer assembly between two substrates brings the contact points on each spring arm into engagement with a pad, elastically bends the contacts and forms redundant high pressure wiped electrical connections between the contact points and pads.

FIELD OF THE INVENTION

[0001] The invention relates to interposer assemblies of the type whichare sandwiched between substrates to form electrical connections betweenopposed pads on the substrates, and to cantilever contacts for formingelectrical connections with contact pads.

BACKGROUND OF THE INVENTION

[0002] Interposer assemblies typically include plastic plates withthrough passages and contacts in the passages for forming electricalconnections between opposed contact pads.

[0003] Interposer assemblies form electrical connections between contactpads arranged in a very close proximity to each other. The pads may bearranged on a one millimeter center-to-center grid. Each assembly mayinclude as many as 961 contacts with four interposer assemblies mountedin a single frame with a total of 3,844 contacts in the frame. Thecontacts must establish reliable electrical connections with the padswhen the assemblies are sandwiched together between circuit members.Failure of a single contact to make a reliable connection renders theentire frame useless.

[0004] Contacts in interposer assemblies include contact surfaces whichmechanically engage the contact pads and form electrical connectionswith the contact pads. Conventional interposer assemblies have singlesurface contacts which engage each pad to form a single electricalconnection with each pad. The contact may wipe along the pad to improvethe quality of the electrical connection. Impurities, oxides orcontaminants on either the contact surface or the pad can impair thesingle surface electrical connections with the pads. Contacts used ininterposer assemblies are typically symmetrical about the center of theinsulating plate, each including a separate spring which biases a singlecontact surface against a pad.

[0005] Accordingly, there is a need for an improved interposer assemblyin which each contact makes redundant contacts with each pad so thatwhen the assembly is sandwiched between overlying and underlyingsubstrates each contact establishes two reliable electrical connectionswith each pad. The connections should have small contact areas toincrease the contact pressure between the contact and the pad. Wipedhigh contact pressure redundant connections would provide reliableinterposer assembly electrical connections. There is also a need for amethod of making a contact with spaced contact points from strip stock,which may be very thin and difficult to form.

[0006] Further, there is need for a spring contact having spaced contactpoints for engaging a contact pad and forming redundant wiped highpressure redundant electrical connections between the contact and thepad.

SUMMARY OF THE INVENTION

[0007] The invention is an improved interposer assembly includingcontacts mounted in passages extending through an insulating plate witheach contact having two contact points on each end of the contact. Whenthe interposer assembly is sandwiched between overlying and underlyingsubstrates the pairs of contact points are brought into wiped pressureengagement with overlying and underlying pads and forms redundantelectrical connections with the pads.

[0008] The contact points are formed on rounded edge corners of thecontacts and have small contact areas, resulting in high contactpressure and reliable electrical connections despite debris, oxides andsurface contaminants on the contacts and pads.

[0009] Each contact includes two tapered spring arms joined to a centralportion. A pair of contact points is formed on the outer end of eachspring arm. The points project above and below the plate. The arms areindependently deflected during compression of the contact by overlyingand underlying substrates. The spring arms may include retention legsextending outwardly from the contact points for engagement with adjacentcam surfaces. Compression of the contacts moves the ends of the legsalong the cam surface to further stress the spring and increase contactforce.

[0010] Additionally, the invention relates to a contact having a beamwith a mounting end and a contact end carrying a pair of laterallyspaced contact points. Movement of a pad against the contact pointsstresses the beam and moves the contact points laterally along the padto form wiped high pressure electrical connections between the contactand the pad. The contact points are rounded edge corners and have a verysmall contact area in order to increase contact pressure and formredundant wiped high pressure electrical connections between the contactand the pad. The contact points are preferably located on opposite sidesof the spring arm and stabilize the contact against twisting.

[0011] Other objects and features of the invention will become apparentas the description proceeds, especially when taken in conjunction withthe accompanying drawings illustrating the invention, of which there arefive sheets of drawings and two embodiments.

DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a top view, broken away, of an interposer assemblyaccording to the invention;

[0013]FIG. 1A is an isometric view of a contact used in the interposerassembly;

[0014]FIG. 2 is a top view of a substrate with pads for formingelectrical connections with the contacts in the interposer assembly;

[0015]FIG. 3 is a sectional view taken along line 3-3 of FIG. 1;

[0016]FIG. 4 is a view like FIG. 3 showing the interposer assemblysandwiched between top and bottom substrates;

[0017]FIG. 5 is an enlarged view of portion of FIG. 4 showing analternative construction;

[0018]FIG. 6 is a view like FIG. 4 showing the substrates engaging theinterposer assembly;

[0019]FIG. 7 is a view like FIG. 2 showing wipe traces on the contactpads of the substrate;

[0020]FIG. 8 is a partially broken away view taken along line 8-8 ofFIG. 6;

[0021]FIG. 9 is a contact perform;

[0022]FIG. 10 is an enlarged view of a portion of the perform of FIG. 9showing a pair of wings;

[0023]FIG. 11 is a sectional view taken along line 11-11 of FIG. 9showing the wings bent upwardly;

[0024]FIG. 12 is a sectional view showing tooling used for punch formingthe preform from strip stock; and

[0025]FIGS. 13 and 14 are sectional views showing a cantilever contactrelated to the interposer contact.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The disclosure relates to the interposer assembly of U.S. Pat.No. 6,176,707, the disclosure of which is incorporated herein byreference in its entirety.

[0027] The disclosure also relates to the interposer assembly ofNeidich, et al. U.S. patent application for “Interposer Assembly,” Ser.No. 09/455,989, filed Jun. 28, 2000, the disclosure of which isincorporated herein by reference, in its entirety.

[0028] The first embodiment interposer assembly 10 includes a flatdielectric plate 12 preferably molded from thermoplastic resin andhaving a plurality of contact passages 14 extending through thethickness of the plate from plate top 16 to plate bottom 18. A contact20 is held in each passage 14. The height of plate 12 may be as littleas 0.048 inches.

[0029] Passages 14 are elongate in transverse cross section. Eachpassage includes a wide end 22, an opposed narrow end 24, a uniformwidth portion 26 adjacent the wide end 22 and a tapered, reduced widthportion 28 adjacent the narrow end. The uniform width portion 26 hasopposed parallel walls extending between the top and bottom of the plateand the reduced width portion has inwardly tapered walls extending fromportion 26 to narrow end 24.

[0030] As illustrated in FIG. 3, a shallow contact-retention projection30 is formed in each narrow passage end 24. The projection is defined byflat upper and lower cam surfaces 32 and 34 extending from projectiontip 36 to the top and bottom of plate 12 respectively. The tip islocated equidistant between the top and bottom of the plate. Both camsurfaces slope away from the tip at a shallow angle of about 12 degreesfrom the vertical. Flat end wall 38 at wide passage end 22 extendsperpendicularly between the top and bottom of plate 12.

[0031]FIG. 5 illustrates a modified interposer assembly plate 12 asimilar to plate 12 and having a top cam surface 32 a and bottom camsurface (not illustrated) which end a short distance 98 inwardly fromthe plate top side 16 a and bottom side (not illustrated). The camsurfaces and short, straight end wall surfaces 98 at the top and bottomsides of the plate extend across the narrow end 24 a of contact passage14 a.

[0032] Plates 12 and 12 a are molded from thermoplastic resin using moldsupporting core pins forming passages 14 and 14 a. The toolingsupporting the core pins normally extends a very short distance into themold cavity to prevent the cam surfaces from extending to the top andbottom of the plate. Each straight surface 98 has a vertical extent ofabout 0.005 inches so that, in practice, the cam surfaces are recessedfrom the top and bottom of the plate only a very small distance. Thisrecess distance does not effect the operation of the interposerassembly.

[0033] Contact 20 is formed from thin uniform thickness metal stripstock, which may be a beryllium copper, and is preferably plated with aconductive metal, which may be gold or a gold alloy, to reduce contactresistance and prevent oxidation. Contacts 20 may be made from stripstock having a thickness of 0.0017 inches. This thin stock is difficultto shape accurately.

[0034] Contacts 20 include a flat central portion or spine 40, likeupper and lower curved and tapered spring arms or beams 42. Arms 42extend in opposite directions from spine 40. Contact noses 44 arelocated at the upper and lower ends of the spring arms. Short, straightand tapered retention legs 46 extending outwardly from the noses andtoward each other to rounded ends 48. When contacts 20 are unstressedthe noses 44 are spaced apart a distance of 0.060 inches, greater thanthe thickness of plate 12. Spring arms 42 are bent laterally away fromcentral spine 40 in the same direction so that noses 44 are locatedbetween the spine and retention leg ends 48. Arms 42 have a maximumwidth adjacent spine 40. The width of each arm decreases from the spineto nose 44. Contacts 20 are symmetrical to either side of spine 40.

[0035] Each spring arm 42 includes a pair of contact points 50 adjacentnose 44. The contact points are spaced apart on opposite sides of thespring arm a short distance inwardly from the nose and project above thesurface of the arm. As shown in FIG. 1, the contact points also arelocated outwardly from the arms to increase the width of the contactadjacent the nose.

[0036]FIG. 9 illustrates preform 52 which is stamped from uniformthickness strip stock and shaped to form contact 20. The preformincludes a central portion 54 which forms spine 40 and two, like arm orbeam sections 56 extending to either side of the central portion whichform arms 42 and legs 46. The widths of the arm sections decrease from amaximum at the central portion to minimums at ends 58. Roundedprojections or wings 60 extend outwardly from the sides of the armsections between the central portion 54 and ends 58.

[0037]FIG. 12 illustrates tooling used to stamping preform 52 from thinstrip stock 62. The strip stock is positioned on anvil 64 with anoverlying pressure plate 66 clamping the strip stock to the anvil.Cutters 68, located to either side of the plate and anvil and abovestrip stock 62, are moved down past the anvil to cut or shear away outerportions 70 of the strip stock from the portion 72 held between theanvil and pressure plate. Sharing forms sheared edges 74 on held portion72 with rounded upper corners 76 and sharp, drag lower corners 78. Inthe drawings, the size of corners 76 and 78 is exaggerated for clarity.

[0038] Stamped preform 52 includes cut edges 74 extending along thesides of both arm sections 56 and around the wings or projections 60 onthe arm sections. Rounded edge corners 76 are located on one side of thepreform and drag corners 78 are located on the other side of thepreform.

[0039] Contact 20 is formed from preform 52 by bending the preform aboutaxes parallel to the plane of the preform to form curved spring arms 42,noses 44, legs 46 and curved ends 48 at the ends of legs 46. The preformis bent to locate rounded edge corners 76 on the outside of the contactand drag corners 78 on the inside of the contact.

[0040] Additionally, during bending of the preform to form the contact,or as an independent step, both projections or wings 60 are bentupwardly relative to the arm sections, around bend lines 80 shown inFIG. 10, to form contact points 50 extending above the spring arms 42adjacent to noses 44. FIG. 7 illustrates the bent up wings with roundedcorners 76 located above the arm section 56 and with the drag corners 78located outwardly and below the rounded corners.

[0041] Contact preform 52 may have a thickness of 0.0017 inches. Metalof this thickness is very hard to handle and shape reliably. The smalldiameter, rounded corners on the contact points are formed duringshearing of the preform from strip stock material without the necessityof physically bending the strip stock. The rounded corners are verysmall having a transverse radius of curvature of about 0.0006 inches to0.0010 depending on tool clearance and wear. It would be very difficultto form these small rounded corners by mechanically shaping the preform.The radius of curvature along the length of the corners is about 0.012inches.

[0042] After bending of preform 52 to form contact 20 as described, thecontact is preferably plated with a conductive metal which may be goldor a gold alloy to form a plating 82 surrounding the contact.

[0043] Formed and plated contacts 20 are inserted into contact passages14 in plate 12 by positioning each contact to one side of a passage witha contact nose located adjacent the center of the passage, spring arms42 adjacent wide passage end 22 and retention legs 46 adjacent narrowpassage end 24. The contact is then moved into the passage to bringspine 40 into engagement with wall 38 and the lead retention leg 46 intoengagement with the adjacent cam surface 32 or 34. This engagementresults because the horizontal distance between the spine and curvedends 48 of legs 46 is greater than the minimum spacing between tip 36and wall 38. Continued movement of the contact into the passageelastically stresses the contact to move the leg inwardly and permitmovement the leg past the projection to the inserted position shown inFIG. 3. After the leg passes the projection tip the contact returns tothe shape shown in FIG. 3. In this position the contact 20 is unstressedand loose in passage 14. Projection 30 extends between the ends of theretention legs 46 to prevent dislodgement of the loose contact from thepassage.

[0044]FIG. 3 shows loose contact 20 with the retention legs away fromthe projection. In practice, gravity will shift the contact down in thepassage so that the upper leg 46 rests on upper top cam surface 32. Withcontact 20 in passage 14 as illustrated, the upper and lower contactnoses 44 are located at the top and bottom of the contact. The contactpoints 50 are also located at the top and bottom of the contact. Noses44 extend across the width of the contact. Projections 50 are located onthe opposed sides of the contact.

[0045] In one interposer assembly 10 having a plate 12 with a thicknessof 0.048 inches and contact 20 formed from uniform thickness strip stockhaving a thickness of 0.0017 inches the height of the unstressedcontacts from nose to nose is 0.060 inches. When the contact ispositioned in a contact passage 14 as shown in FIG. 3 each contact nose44 projects a distance 0.006 inches above the top or bottom side of theplate. The contact points 50 are spaced apart across the width of thecontact 0.0115 inches.

[0046] Interposer assembly 10 is used to establish electricalconnections between opposed contact pads 84 on substrates 86 located toeither side of the assembly. FIG. 2 illustrates the contact surface of asubstrate 86 with pads 84. FIG. 4 illustrates the interposer assembly 10located between substrates 86 with the contact pads 84 lightly engagingthe contact noses 44 and contact points 50 on each end of contacts 20 inpassage 14 with contact 20 unstressed.

[0047]FIG. 6 illustrates interposer assembly 10 fully sandwiched betweensubstrates 86 with the contact pads 84 on the substrates engaging thetop and bottom plate surfaces and contact 20 collapsed into passage 14.During movement of the substrates onto the plate each contact nose iscollapsed 0.006 inches into the passage, the rounded ends of theretention legs 46 are brought into engagement with the upper and lowercam surfaces 32 and 34 and are moved inwardly along the surfaces to theposition shown in FIG. 3 adjacent tip 36. As the contact is collapsed,the retention legs 46 and the spring arms 42 are bent laterallyelastically to provide high contact pressure between the ends of thecontact and the pads 84 and to wipe the points along the pads. Thespring arms 42 and central portion or spine 40 form an elastic springsystem. In this position, contacts 20 are held in the passages by thesubstrates.

[0048] As contact 20 is collapsed into passage 14 the ends of arms 43rotate and engagement between the outer ends of the arms and pads 84moves along the arms from noses 44 to the adjacent rounded corners 76 atthe tops of the contact points 50. Compare FIGS. 4 and 6. The roundededge corners 76 at the tops of the contact points 50 wipe along pads 84to form wipe traces 88 shown in FIG. 7. Each trace 88 extends from apoint of initial contact 90 between a point 50 and the pad to a finalcontact position 92. The contact points move along traces 88 in adirection away from passage wide end 22 and toward passage narrow end24. The resiliency of the stressed spring system biases the small arearounded corners 76 of points 50 against the contact pads under highpressure as the points are moved along traces 88. The contact pressureexerted by the spring system is applied to the pads at the small fourrounded corners 76 of points 50, resulting in redundant high pressureelectrical connections between the points and pads. The contactpressures are high because the contact areas are low. High pressurewiped engagement between the points 50 and the pads breaks throughdebris, oxides or other surface contaminants on the points or on thepads. The rounded corners slide along, but do not cut into the pads. Theprovision of redundant contacts at each end of contacts 20 increases thereliability of electrical connection between contact 20 and pads 84 overconventional single area contacts.

[0049] During compression of contacts 20 into passages 14 the twocontact arms 44 are each bent away from wide passage end 22independently of each other with contact central portion or spine 40held on end wall 22, although the contact may shift vertically a slightdistance in the passage to shift the spine up or down along wide endwall 22. Each arm 42 is stressed essentially independently of the otherarm 42 so that the contact pressure at points 50 on one end of thecontact is provided by elastic deformation of the adjacent spring arm 42and retention leg 46, located to one side of the central portion. Thus,contact 20 includes two like spring contacts each located to one side ofthe central portion and each including a curved tapered spring arm 42and a tapered retention leg 46. The width of retention leg 46 decreasesfrom nose 44 to end 48 to permit ready deflection of the leg by theadjacent cam surface 32 or 34. Deflection of both the spring arm 42 andleg 46 contribute to the spring force holding projections 50 againstadjacent pad 84. Each of the independent, like spring contacts providesan electrical connection between a contact pad and the spine 40 at thecenter of contact 20.

[0050]FIGS. 13 and 14 illustrate a cantilever spring contact 100 formedfrom bent uniform thickness strip stock, related to contact 20. Thestrip stock may have a desired thickness, which may be other than thethickness of contact 20. The contact 100 includes a mounting end 102 anda contact end 108. End 102 is mounted in substrate 104. A curved,tapered spring arm or beam 106 extends upwardly from the substrate andis bent laterally to one side of the mounting end 102. The mounting endis connected to a circuit element (not illustrated). Contact 100connects the circuit element to pad 114 on substrate 112.

[0051] Spring arm 106 may be identical to spring arm 42 in contact 20and is a beam having a tapered width decreasing from a maximum width atmounting end 102 to a minimum width at contact end or end 108. A pair ofcontact points 110 having upwardly facing rounded edge corners areformed on the opposite sides of arm 106 at end 108. Arm 106, end 108 andcontact points 110 may be identical to arm 42, nose 44 and contactpoints 50 of contact 20, previously described.

[0052]FIG. 13 illustrates substrate 112 located above substrate 104 andcarrying contact pad 114. Pad 114 engages end 108 and points 110 ofcontact 100 without stressing the contact.

[0053] Electrical connections are established between pad 114 andcontact 100 by reducing the distance between substrates 104 and 112 sothat the spring arm 106 is elastically bent laterally and engagementbetween the contact and the pad shifts from end 108 to the roundedcorners of spaced contact points 110, in the same way redundant contactsare established between the ends of the spring arms 42 in contact 20 andoverlying and underlying pads 84.

[0054] Elastic bending of the spring arm provides high contact pressureengagement between the points 110 and pad 114. The points are wipedalong the pad to form contact traces on the pad like traces 88 shown inFIG. 7. The wiped, redundant high pressure contacts between the contactand pad assure reliable low resistance electrical connections areestablished. The spaced apart contact points 110 support contact 100 onpad 114 to prevent twisting of the contact.

[0055] Contact 100 does not include a leg and curved end like retentionleg 46 and curved end 48 of contact 20. If desired, contact 100 may beprovided with a leg 116 having a curved end 118, like leg 46 and end 48,and substrate 104 may be provided with a cam surface 120, like top camsurface 32 in plate 2. Leg 116, end 118 and cam surface 120 are shown indashed lines in FIGS. 13 and 14. During collapse of spring 100 providedwith a leg 116 and end 118, end 118 engages cam surface 120, leg 116 iselastically deformed and increases the contact pressure between points102 and pad 114. The spring arm 110 with arm 116 and end 118 is deformedidentically to each half of contact 20 as the overlying and underlyingsubstrates 86 are moved together from the position of FIG. 4 to theposition of FIG. 6.

[0056] While I have illustrated and described a preferred embodiment ofmy invention, it is understood that this is capable of modification, andI therefore do not wish to be limited to the precise details set forth,but desire to avail myself of such changes and alterations as fallwithin the purview of the following claims.

What I claim as my invention:
 1. An interposer assembly for formingredundant electrical connections with contact pads on substratespositioned above and below the assembly, said assembly comprising: a) aninsulating plate having top and bottom sides and a plurality of passagesextending through the thickness of the plate; and b) a plurality ofmetal contacts, each contact disposed in one of said passages, eachcontact including a first pair of spaced contact points at the top sideof the plate, a second pair of spaced contact points at the bottom sideof the plate, and a spring portion extending between said first pair ofcontact points and said second pair of contact points, said springportion spacing said pairs of contact points apart a distance greaterthan the thickness of the plate when the spring portion is unstressed,wherein each pair of contact points forms redundant electricalconnections with a contact pad on a substrate.
 2. The assembly as inclaim 1 wherein in each contact the contact points of each pair ofcontact points are spaced laterally across the contact.
 3. The assemblyas in claim 2 wherein each contact point comprises a rounded corner. 4.The assembly as in claim 3 wherein each contact is formed from uniformthickness strip stock having a sheared circumferential edge, and eachcontact point is located on a corner of said circumferential edge. 5.The assembly as in claim 4 wherein each spring portion includes acentral portion and a pair of beams, each beam located between thecentral portion and a pair of contact points, said beams elasticallybendable into said passages.
 6. The assembly as in claim 5 wherein eachcontact point is bent to one side of a beam.
 7. The assembly as in claim6 wherein each contact point is rounded along the length of the edgecorner.
 8. The assembly as in claim 7 wherein said strip stock has athickness of about 0.0017 inches.
 9. The assembly as in claim 7 whereinsaid rounded corners have a transverse radius of curvature of about0.0006 to 0.0010 inches.
 10. The assembly as in claim 7 wherein eachcontact is symmetrical to either side of the central portion.
 11. Theassembly as in claim 10 wherein the plate includes a projectionextending into each passage, and each contact includes two retentionportions located on opposite sides of a projection to retain the contactin the passage.
 12. The assembly as in claim 1 wherein each contactincludes opposed sheared edges, each contact point comprising a shearrounded edge corner.
 13. The assembly as in claim 12 wherein eachcontact point comprises a bent projection.
 14. An assembly adapted to beinterposed between pairs of spaced metallic pads on substrates forforming electrical connections between the pads, said assemblycomprising: a) a dielectric plate having a top and a bottom, a pluralityof spaced passages extending through the thickness of the plate fromsaid top to said bottom thereof, said passages each including opposedinterior walls, b) a projection in each passage, each projectionextending outwardly from one of said interior walls toward an opposedinterior wall and including a first surface facing said plate top and asecond surface facing said plate bottom; c) a plurality of metalcontacts, each contact disposed in one of said passages, each contactformed from thin sheet metal stock and including a central portion, apair of beams extending to either side of the central portion, a noselocated on the end of each beam, and a retention leg extending inwardlyfrom each nose to an end located away from the central portion, saidnoses spaced apart a distance greater than the thickness of the platewhen the contact is unstressed, each contact being located in a passagewith the central portion adjacent an interior wall away from the passageprojection and the ends of the retention legs located on opposite sidesof the projection so that the projection retains the contact in thepassage; and d) each contact including a pair of laterally spacedcontact points adjacent each contact nose; e) wherein upon compressionof the contacts into the passages by opposed contact pads, the beams arestressed, and the contact points on each nose engage and wipe along apad to form redundant wiped pressure connections with the pad.
 15. Theassembly as in claim 14 wherein said beams are curved.
 16. The assemblyas in claim 15 wherein each contact point is located on an edge of abeam adjacent a nose.
 17. The assembly as in claim 16 wherein eachcontact point is located at a corner of a beam edge.
 18. The assembly asin claim 16 wherein each contact point comprises a shear-wiped corner ofa beam edge.
 19. The assembly as in claim 18 wherein said strip stockhas a thickness of about 0.0017 inch.
 20. The assembly as in claim 19wherein said contact points are rounded and have a radius of curvatureof about 0.006 inches.
 21. The assembly as in claim 18 wherein eachcontact point comprises a portion of a contact bent to one side of theremainder of the contact.
 22. The assembly as in claim 15 wherein saidbeams are tapered.
 23. The assembly as in claim 22 wherein saidretention legs are tapered.
 24. A spring contact for forming redundantelectrical connections with a contact pad, said spring contactcomprising an elongate metal body including a mounting end, a contactend and a resilient beam located between such ends, the beam extendinglaterally away from the mounting end to locate the contact end to oneside of the mounting end, said contact end including a pair of contactpoints spaced across the contact end, wherein movement of a contact padinto engagement with contact points flexes the beam and wipes thecontact points along the pad to form redundant pressure electricalconnections between the contact and pad.
 25. The spring contact as inclaim 24 wherein each contact point comprises a rounded edge.
 26. Thespring contact as in claim 25 wherein the spring contact is formed fromuniform thickness strip stock having a sheared circumferential edge, andeach contact point is located on a corner of said circumferential edge.27. The spring contact as in claim 26 wherein each contact point is bentto one side of the contact ends.
 28. The spring contact as in claim 27wherein each contact point is rounded along the length of the edgecorner.
 29. An interposer assembly for forming redundant electricalconnections with contact pads on substrates positioned above and belowthe assembly, said assembly comprising: a) an insulating plate havingtop and bottom sides and a plurality of passages extending through thethickness of the plate; and b) a plurality of metal contacts, eachcontact disposed in one of said passages, each metal contact comprisingan integral body formed from uniform thickness strip stock and includinga first spring contact as in claim 24 and a second spring contact as inclaim 24, each metal contact including a central portion joining themounting portions of said spring contacts, the contact portions of saidspring contacts facing outwardly of the passage at the top and bottomthereof, the contact portions spaced apart a distance greater than thethickness of the plate when the metal contact is unstressed, wherein thecontact points on each contact end form redundant electrical connectionswith a contact pad on a substrate.
 30. An interposer assembly as inclaim 29 wherein said beams are curved.
 31. An interposer assembly as inclaim 30 wherein each contact point comprises a rounded corner.
 32. Aninterposer assembly as in claim 31 wherein each rounded corner islocated on a sheared edge of the metal contact.
 33. An interposerassembly as in claim 32 wherein each contact point is bent up from oneside of a contact end.
 34. An interposer assembly as in claim 33 whereineach contact point is rounded along the length of the edge corner. 35.The method of making a spring contact for forming redundant electricalconnections with a contact pad, comprising the steps of: a) cutting apreform from a strip of uniform thickness metal stock to form a preformhaving a circumferential edge and edge corners; b) rounding one edgecorner to form a pair of adjacent contact surfaces; and c) bending thepreform to locate the contact surfaces to one side of the preform toform two spaced apart contact points.
 36. The method of claim 35including the step of: d) bending the preform away from the contactpoints to form a resilient beam.
 37. The method of claim 35 includingthe step of: e) rounding the edge corners of said contact points alongthe lengths thereof.